1. Field of the Invention
This invention relates to can bodies of the type that include a sidewall having flutes or grooves defined therein, and to a method and apparatus for making such can bodies using the draw-redraw process that is typically used for making 2-piece can bodies.
2. Description of the Related Technology
Features such as ribs and flutes in the sidewalls of can bodies have long been known, and have been used for several reasons. One reason is to give an interesting appearance to the can body which may promote a brand image, as is discussed in U.S. Pat. No. 5,938,389 to Shore et al. Longitudinal ribs and panels have also been used to impart additional rigidity to the sidewall against loads applied to the top of the can body, such as arise during double seaming of a can end to close the body, or during stacking of filled cans. This is more fully discussed in U.S. Pat. No. 5,699,932.
The process of making can bodies using the draw-redraw forming technique has been in commercial use for decades. This process is accomplished by performing a first draw to create a cup having a large diameter and then performing a second draw using the preformed cup so that a punch is relatively moved into engagement with a redrawing die. An annular cup-holding member is arranged within the preliminarily drawn cup, and a bottom face of the preliminarily drawn cup is held by the holding member and the flat face portion of the redrawing die. At the redrawing step, the holding member is moved synchronously with the redrawing die. In this structure, at the relative movement of the punch and the die, the preliminarily drawn cup is draw-formed into a deep-draw-formed cup having a small diameter by a curvature comer portion of the redrawing die and simultaneously, the side wall of the preliminarily drawn cup is bent and elongated and the thickness of the side wall is reduced. At the deep-draw forming, the holding member and the flat face portion of the redrawing die act as the blank holding face to a portion of the cup on which influences of the plastic flow are imposed.
Companies that package food products and other articles in two piece cans often prefer a bottom configuration that has what is known in the industry as a xe2x80x9cbump-up.xe2x80x9d A bump-up bottom is characterized as having a downwardly facing annular projection in the outer circumferential area at which it is coextensive with the container sidewall. Bump-up bottoms may also have similar, concentric annular projections that are positioned in the interior of the container bottom, radially inward from the major projection.
The inventors have for some time been attempting to create a viable draw-redraw manufacturing process for two piece cans having a bump-up bottom and axial ribs in the sidewall, but have experienced the problem that the axial ribs tend to be drawn into the major projection of the bump up bottom. For aesthetic and other reasons, this is unacceptable. A need exists for an improved manufacturing process for two piece cans of the type having a bump-up bottom and axial sidewall ribs that ensures ample material in the bottom area of the can body preform so as to prevent the sidewall ribs from being drawn into the bump-up area.
It is, accordingly, an object of the invention to provide an improved manufacturing process for two piece cans of the type having a bump-up bottom and axial sidewall ribs that ensures ample material in the bottom area of the can body preform so as to prevent the sidewall ribs from being drawn into the bump-up area.
In order to achieve the above and other objects of the invention, a method of making a can body of the type that has at least one axially extending rib formed therein includes, according to a first aspect of the invention, steps of performing a first drawing operation to create a cup having a sidewall that has at least one axially extending rib formed therein and a bottom that is coextensive with the sidewall and intersects the sidewall at a rim, this step being performed so that at least a portion of the bottom is recessed by a predetermined depth with respect to the rim; and performing a second drawing operation on the cup to form a can body having a bump-up bottom, and wherein the predetermined depth is sufficient so as to prevent the axially extending rib to be drawn into the bump-up bottom.
According to a second aspect of the invention, a method of making a can body of the type that has at least one axially extending rib formed therein includes steps of providing a cup having a sidewall and a bottom that is coextensive with the sidewall and intersects the sidewall at a rim, this step being performed so that at least a portion of the bottom is recessed by a predetermined depth with respect to the rim; and performing a forming operation on the cup to form a can body having at least one axial rib defined in its sidewall and having a bump-up bottom, and wherein the predetermined depth is sufficient so as to prevent the axially extending rib to be drawn into the bump-up bottom during the forming operation.
These and various other advantages and features of novelty that characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention.